BQ27510_08 Datasheet, PDF (26/36 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Direct Battery Connection

bq27510
SLUS816A – MARCH 2008 – REVISED JUNE 2008.......................................................................................................................................................... www.ti.com
NORMAL Mode
The fuel gauge is in NORMAL Mode when not in any other power mode. During this mode, AverageCurrent( ),
Voltage( ) and Temperature( ) measurements are taken, and the interface data set is updated. Decisions to
change states are also made. This mode is exited by activating a different power mode.
Because the gauge consumes the most power in NORMAL mode, the Impedance Track™ algorithm minimizes
the time the fuel gauge remains in this mode.
SLEEP Mode
SLEEP mode is entered automatically if the feature is enabled (Operation Configuration [SLEEP]) = 1) and
AverageCurrent( ) is below the programmable level Sleep Current. Once entry into SLEEP mode has been
qualified, but prior to entering it, the bq27510performs an ADC autocalibration to minimize offset.
During SLEEP mode, the bq27510 periodically takes data measurements and updates its data set. However, a
majority of its time is spent in an idle condition.
The bq27510 exits SLEEP if any entry condition is broken, specifically when (1) AverageCurrent( ) rises above
Sleep Current, or (2) a current in excess of I_WAKE through R_SENSE is detected.
In the event that a battery is removed from the system while a charger is present (and powering the gauge),
Impedance Track™ updates are not necessary. Hence, the fuel gauge enters a state that checks for battery
insertion and does not continue executing the Impedance Track™ algorithm.
BAT INSERT CH ECK Mode
This mode is a halted-CPU state that occurs when an adapter, or other power source, is present to power the
bq27510 (and system), yet no battery has been detected. When battery insertion is detected, a series of
initialization activities begin, which include: OCV measurement, setting the BAT_GD pin, and selecting the
appropriate battery profiles. The battery insertion detection takes about 3ms.
Some commands, issued by a system processor, can be processed while the bq27510 is halted in this mode.
The gauge will wake up to process the command, then return to the halted state awaiting battery insertion.
HIBERNATE Mode
HIBERNATE mode should be used when the system equipment needs to enter a very low-power state, and
minimal gauge power consumption is required. This mode is ideal when a system equipment is set to its own
HIBERNATE, SHUTDOWN, or OFF modes. The fuel gauge can enter HIBERNATE due to either low cell voltage
or low load current.
• HIBERNATE due to the cell voltage. When the cell voltage drops below the Hibernate Voltage and a valid
OCV measurement has been taken, the fuel gauge enters HIBERNATE mode The [HIBERNATE] bit of the
CONTROL register has no impact for the fuel gauge to enter the HIBERNATE mode.
• HIBERNATE due to the load current. If the fuel gauge enters the HIBERNATE mode due to the load current,
the [HIBERNATE] bit of the CONTROL_STATUS register must be set. The gauge waits to enter HIBERNATE
mode until it has taken a valid OCV measurement and the magnitude of the average cell current has fallen
below Hibernate Current.
The gauge will remain in HIBERNATE mode until the system issues a direct I2C command to the gauge or a
POR occurs. I2C Communication that is not directed to the gauge will not wake the gauge (or at least for very
long).
During Hibernate mode the /BAT_GD signal is negated (no battery charging/discharging). This prevents a
charger application from inadvertently charging the battery before an OCV reading can be taken. It is the
system’s responsibility to wake the bq27510 after it has gone into HIBERNATE mode. After waking, the gauge
can proceed with the initialization of the battery information (OCV, profile selection, etc.)
It is suggested to keep the system in the SLEEP mode instead of HIBERNATE mode when a charger is
attached. The reason is that charger removal will not wake up the battery from HIBERNATE mode.
26
Submit Documentation Feedback
Product Folder Link(s): bq27510
Copyright © 2008, Texas Instruments Incorporated